U.S. patent application number 12/180195 was filed with the patent office on 2010-01-28 for kvm system.
This patent application is currently assigned to ATEN INTERNATIONAL CO., LTD.. Invention is credited to Yi-Li LIU.
Application Number | 20100023660 12/180195 |
Document ID | / |
Family ID | 41569633 |
Filed Date | 2010-01-28 |
United States Patent
Application |
20100023660 |
Kind Code |
A1 |
LIU; Yi-Li |
January 28, 2010 |
KVM SYSTEM
Abstract
A keyboard-video-mouse (KVM) system is disclosed. The KVM system
comprises a module, a KVM switch and a signal cable. The module
transmits a single-ended video signal from a computer, converts a
universal asynchronous receiver/transmitter (UART) signal to an
input/output (IO) signal, and transmits the IO signal to the
computer. The KVM switch receives the single-ended video signal
from the module and outputs the UART signal to the module. The
signal cable transmits the single-ended video signal from the
module to the KVM switch and transmits the UART signal from the KVM
switch to the first module.
Inventors: |
LIU; Yi-Li; (Taipei City,
TW) |
Correspondence
Address: |
Patterson & Sherldan - ATEN
3040 Post Oak Boulevard, Suite 1500
Houston
TX
77056
US
|
Assignee: |
ATEN INTERNATIONAL CO.,
LTD.
Shijr City
TW
|
Family ID: |
41569633 |
Appl. No.: |
12/180195 |
Filed: |
July 25, 2008 |
Current U.S.
Class: |
710/71 ;
710/65 |
Current CPC
Class: |
G06F 3/1423 20130101;
G06F 3/023 20130101; G09G 2370/24 20130101; G06F 3/14 20130101;
G09G 2370/047 20130101; G06F 3/038 20130101 |
Class at
Publication: |
710/71 ;
710/65 |
International
Class: |
G06F 13/38 20060101
G06F013/38 |
Claims
1. A keyboard-video-mouse (KVM) system, comprising: a first module,
transmitting at least one single-ended video signal from a
computer, converting at least one universal asynchronous
receiver/transmitter (UART) signal to an input/output (IO) signal
and transmitting the IO signal to the computer; a KVM switch,
receiving the single-ended video signal from the first module and
outputting the UART signal to the first module; and a first signal
cable, transmitting the single-ended video signal from the first
module to the KVM switch, and transmitting the UART signal from the
KVM switch to the first module.
2. The KVM system of claim 1, further comprising a console
outputting the IO signal to the KVM switch and receiving the
single-ended video signal from the KVM switch.
3. The KVM system of claim 2, wherein the IO signal from the
console and/or the single-ended video signal from the computer are
accessible to a network.
4. The KVM system of claim 1, further comprising: a second module,
transmitting the single-ended video signal from the KVM switch,
converting the input/output (IO) signal into the UART signal and
transmitting the UART signal to the KVM switch; a second signal
cable, transmitting the single-ended video signal from the KVM
switch to the second module, and transmitting the UART signal from
the second module to the KVM switch; and a console, outputting the
IO signal to the second module and receiving the single-ended video
signal from the second module.
5. The KVM system of claim 1, wherein the single-ended video signal
comprises a R-signal, a G-signal, a B-signal, a H-Sync signal and a
V-sync signal and the first signal cable comprises five wires
separated for transmitting the R-signal, the G-signal, the
B-signal, the H-Sync signal and the V-sync signal
corresponsively.
6. The KVM system of claim 1, wherein the first signal cable
comprises two wires untwisted and separated for transmitting the
UART signal by utilizing non-differential signaling
transmission.
7. The KVM system of claim 1, wherein the first signal cable
comprises two wires twisted for transmitting the UART signal by
utilizing differential signaling transmission.
8. The KVM system of claim 1, wherein the first module comprises a
first signal converter for converting the UART signal to the IO
signal.
9. The KVM system of claim 2, wherein the KVM switch comprises a
second signal converter for converting the IO signal from the
module to the UART signal.
10. The KVM system of claim 1, wherein the IO signal is selected
from a group consisting of a keyboard signal, a mouse signal, a
storage data signal and an audio signal.
11. A keyboard-video-mouse (KVM) switch coupling a number of
computers to at least one console, comprising: a video switch,
switching to one of the computers and routing at least one
single-ended video signal from the computer to the console; a
controller, controlling at least one input/output (IO) signal from
the console; and a signal converter, converting the IO signal from
the controller into a universal asynchronous receiver/transmitter
(UART) signal and signaling the UART signal to the computer.
12. The KVM switch of claim 11, wherein the UART signal is signaled
by utilizing non-differential signaling.
13. The KVM switch of claim 11, wherein the UART signal is signaled
by utilizing differential signaling.
14. A keyboard-video-mouse (KVM) extender, comprising: a local
unit, transmitting a single-ended video signal from a computer,
converting a universal asynchronous receiver/transmitter (UART)
signal to an input/output (IO) signal and transmitting the IO
signal to the computer; a remote unit, transmitting the
single-ended video signal from the local unit to a console, and
outputting the UART signal to the local unit ; and a signal cable,
transmitting the single-ended video signal from the local unit to
the remote unit, and transmitting the UART signal from the remote
unit to the local unit.
15. The KVM extender of claim 14, wherein the single-ended video
signal comprises a R-signal, a G-signal, a B-signal, a H-Sync
signal and a V-sync signal and the signal cable comprises five
wires separated for transmitting the R-signal, the G-signal, the
B-signal, the H-Sync signal and the V-sync signal
corresponsively.
16. The KVM extender of claim 14, wherein the signal cable
comprises two wires separated for transmitting the UART signal by
utilizing non-differential signaling transmission.
17. The KVM extender of claim 14, wherein the signal cable
comprises two wires twisted for transmitting the UART signal by
utilizing differential signaling transmission.
18. A keyboard-video-mouse (KVM) system, for coupling a console to
at least one computer, the console sending a plurality of parallel
signals for controlling the computer, the KVM system comprising: a
KVM switch, converting the plurality of parallel signals into a
bi-directional serial signal in differential mode; a module,
converting the bi-directional serial signal in differential mode
into the plurality of parallel signals for controlling the
computer; wherein the module further transmitting at least one
single-ended video signal from the computer to the KVM switch; and
wherein the KVM switch further transmitting the at least one
single-ended video signal to the console.
19. The KVM system of claim 18, further comprises a signal cable,
for connecting the module to the KVM switch, and transmitting the
bi-directional serial signal in differential mode and the at least
one single-ended video signal.
20. The KVM system of claim 19, wherein the signal cable further
comprises a first RJ-45 male connector at a first end for
connecting the KVM switch and a second RJ-45 male connector at a
second end for connecting the module.
21. The KVM system of claim 19, wherein the signal cable further
comprises a pair of twisted wires for carrying the bi-directional
serial signal in differential mode and 6 separate wires for
carrying the at least one single-ended video signal.
22. The KVM system of claim 20, wherein the KVM switch farther
comprises a plurality of RJ-45 connecting ports to match the first
end of the signal cable.
23. The KVM system of claim 22, wherein the KVM switch further
comprises height not more than 1U.
24. The KVM system of claim 23, wherein the KVM switch further
comprises at least 32 RJ-45 connecting ports.
25. A keyboard-video-mouse (KVM) system, for coupling a console to
at least one computer, the console sending a plurality of parallel
signals for controlling the computer, the KVM system comprising: a
KVM switch, converting the plurality of parallel signals into at
least one uni-directional serial signal; a module, converting the
unidirectional serial signal into the plurality of parallel signals
for controlling the computer; wherein the module further
transmitting at least one single-ended video signal from the
computer to the KVM switch; and wherein the KVM switch further
transmitting the at least one single-ended video signal to the
console.
26. The KVM system of claim 25, further comprises a signal cable,
for connecting the module to the KVM switch, and transmitting the
uni-directional serial signal and the at least one single-ended
video signal.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to a keyboard-video-mouse
(KVM) system, and more particularly, to communication in the KVM
system.
BACKGROUND OF THE INVENTION
[0002] Communication between a KVM switch and a module (e.g. a
dongle) is an important part for designing a KVM system. It has to
take many aspects into consideration, such as signal cable,
connector, signal converter, and transmitting distance etc. For a
well designed KVM system, video signals, keyboard (KB) signals, and
mouse (MS) signals can be transmitted therebetween properly.
[0003] Here provided two main conventional techniques, D-sub 15
(15-pin VGA connector) based KVM device communication and category
5 (CAT 5) based KVM device communication. Generally, a KVM system
utilizing D-sub 15 based KVM device communication is called an
analog KVM system in which a common 15-pin VGA connector is often
used. Since the size of 15-pin VGA connector is too large, it is
not easy to connect much more computers. Generally, a KVM switch
can connect at most 16 computers in a 1U system rack if D-sub 15
connectors are used to interface the KVM switch and computers. This
may not serve the needs of IT administrators in large corporations.
Moreover, a D-sub 15 cable can be 3-in-1. The 3-in-1 D-sub 15 cable
provides not only five wires for transmitting video signals but
also another five wires for transmitting KB data signals, KB clock
signals, KB power signals, MS data signals, and MS clock signals
corresponsively, and thus complicate the main board circuit of KVM
switch. If a field-programmable gate array (FPGA) is used, a more
complicated FPGA will be needed. Furthermore, the 3-in-1 D-sub 15
cable does not transmit USB storage data signals and audio
signals.
[0004] The conventional CAT 5 based KVM device communication is
disclosed in U.S. Pat. No. 6,137,455. For a CAT 5 based KVM device,
because RJ-45 connectors are used, which smaller than 15-pin VGA
connectors, the KVM switch can connect up to 32 computers in a 1U
system rack. However, one of the disadvantages of KVM system
utilizing CAT 5 based KVM device communication is that a video
encoder circuit and a video decoder circuit are needed. As
following, a CAT 5 based KVM system and its disadvantages of
needing video encoder and decoder circuits will be described.
[0005] Please refer to FIG. 1a. Through a CAT 5 based KVM system, a
computer 11 is communicated with a console 12 by transmitting a
video signal and an input/output (IO) signal, e.g. a KB signal
and/or a MS signal. The CAT 5 based KVM system comprises a module
18, a KVM switch 19 and a CAT 5 cable 13. The video signal from the
computer 11 is encoded by a video encoder circuit 171 of the module
18 and then transmitted in the CAT 5 cable 13 to a video decoder
circuit 172 of the KVM switch 19. The encoded video signal is
decoded by the video decoder circuit 172 and then transmitted to
the console 12. In the KVM switch 19, the IO signal from the
console 12 is controlled by a controller 161 and converted to a
universal asynchronous receiver/transmitter (UART) signal by the
signal converter 169. The UART signal is transmitted in the CAT 5
cable 13, converted to the IO signal by the signal converter 159.
The IO signal is controlled by a controller 151 in the module 18,
and then transmitted to the computer 11.
[0006] Please refer to FIG. 1b. The CAT 5 cable 13 has 4 pair of
wires, each pair twisted. The video signal and the IO signal are
transmitted by utilizing differential signaling transmission. The
video signal can be a VGA signal, which comprises R, G, B, H-Sync,
and V-sync signals. By differential signaling, the R-signal is
signaled as R.sub.+ and R.sub.- in a twisted pair as shown.
Similarly, the G-signal is signaled as G.sub.+ and G.sub.-, the
R-signal as R.sub.+ and R.sub.-. The H-Sync signal and the V-sync
signal are included when signaling the RGB signal. In addition, the
IO signal is converted into the UART signal, which is signaled as
U.sub.+ and U.sub.- in the last twisted pair also by differential
signaling. Therefore, the video signal and the IO signal are
transmitted.
[0007] Since the video signal is transmitted by utilizing
differential signaling transmission in the CAT 5 based KVM system,
requirement of the video encoder circuit 171 and the video decoder
circuit 172 is inevitable. Therefore, video encoder and decoder
circuits not only increase the cost of modules and KVM switches,
but also increase the response time of video signal to result in a
bad performance.
[0008] Accordingly, the present invention provides a solution to
overcome the above-mentioned disadvantages.
SUMMARY OF THE INVENTION
[0009] To solve the foregoing disadvantages in the conventional
techniques, an objective of the present invention is to transmit
single-ended video signals in a keyboard-video-mouse (KVM) system
directly rather than encode/decode video signals or differential
video signals.
[0010] Based on the aforesaid objective, an aspect of the present
invention is to provide a KVM system. The KVM system comprises a
module, a KVM switch and a signal cable. The module transmits a
single-ended video signal from a computer, converts a universal
asynchronous receiver/transmitter (UART) signal transmitted from
the KVM to an input/output (IO) signal, and transmits the IO signal
to the computer. The KVM switch outputs the UART signal to the
module, and receives the single-ended video signal from the
computer via the module and the signal cable. The signal cable
connects the KVM switch to the module for transmitting the
single-ended video signal from the module to the KVM switch and
transmitting the UART signal from the KVM switch to the module. The
signal cable has a first RJ-45 male connector at its first end for
connecting the KVM and a second RJ-45 male connector at its second
end for connecting the module. On the other hand, the KVM switch
has a plurality of RJ-45 female connectors to match the first end
of the signal cable. The signal cable further has 8 signal wires
for carrying the single-ended video signals and UART signal. At
least 6 of the 8 signal wires are untwisted and separated.
[0011] Another aspect of the present invention is to provide a KVM
switch. The KVM switch, which couples a number of computers to at
least one console, comprises a video switch, a controller and a
signal converter. The video switch switches to one of the computers
and routes a single-ended video signal from the computer to the
console. The controller manages and processes at least one IO
signal from the console. The signal converter converts the IO
signal from the controller into an UART signal and signals the UART
signal to the computer.
[0012] Another aspect of the present invention is to provide a KVM
extender, which allows access to a computer from a remote console
in the distance. The KVM extender comprises a local unit, a remote
unit and a signal cable. The local unit transmits a single-ended
video signal from a computer, converts an UART signal to an IO
signal, and transmits the IO signal to the computer. The remote
unit transmits the single-ended video signal from the local unit to
the remote console and outputs the UART signal to the local unit.
The signal cable transmits the single-ended video signal from the
local unit to the remote unit and transmits the UART signal from
the remote unit to the local unit.
[0013] Another aspect of the present invention is to provide a KVM
system such as matrix KVM system, which allows multiple users
control computers simultaneously and independently. The computers
can be connected through a combination of multiple matrix KVM
switches. In matrix KVM system, for example, a computer couples a
first module, a matrix KVM switch and a second module to a console.
The first module transmits a single-ended video signal from a
computer, converts an UART signal to an IO signal, and transmits
the IO signal to the computer. The KVM switch receives the
single-ended video signal from the first module and outputs the
UART signal to the first module. A first signal cable transmits the
single-ended video signal from the first module to the KVM switch
and transmits the UART signal from the KVM switch to the first
module. The second module transmits the single-ended video signal
from the KVM switch, converts the IO signal into the UART signal,
and transmits the UART signal to the KVM switch. A second signal
cable transmits the single-ended video signal from the KVM switch
to the second module and transmits the UART signal from the second
module to the KVM switch. A console outputs the IO signal to the
second module and receives the single-ended video signal from the
second module.
[0014] Another aspect of the present invention is to provide a KVM
system, which couples a console to at least one computer, and the
console sends a plurality of parallel signals for controlling the
computer. The KVM system comprises a KVM switch and a module. The
KVM switch converts the parallel signals into a bi-directional
serial signal in differential mode. The module converts the
bi-directional serial signal in differential mode into the parallel
signals for controlling the computer. Furthermore, the module
transmits at least one single-ended video signal from the computer
to the KVM switch. The KVM switch transmits the at least one
single-ended video signal to the console.
[0015] Another aspect of the present invention is to provide a KVM
system, which couples a console to at least one computer, and the
console sends a plurality of parallel signals for controlling the
computer. The KVM system comprises a KVM switch and a module. The
KVM switch converts the parallel signals into at least one
uni-directional serial signal. The module converts the
uni-directional serial signal into the parallel signals for
controlling the computer. Furthermore, the module transmits at
least one single-ended video signal from the computer to the KVM
switch. The KVM switch transmits the at least one single-ended
video signal to the console.
[0016] According to the present invention, the single-ended video
signal is directly transmitted from the computer to the console.
That is, it does not need to encode/decode the video signal. Thus,
video encoder/decoder circuits can be eliminated. The cost of
producing KVM devices such as modules, KVM switches, KVM extenders
or matrix KVM switches, is thereby reduced.
[0017] According to the present invention, the IO signal such as a
keyboard (KB) signal, a mouse (MS) signal, an USB storage data
signal and an audio signal, all are able to be transmitted. All
aforesaid signals are converted to the UART signal, which can be
transmitted in only two wires of the signal cable. Compared to the
conventional D-sub 15 based KVM device, the main board circuit of
KVM device in accordance with the present invention is much
simpler. If a field-programmable gate array (FPGA) is used, a much
cheaper FPGA is enough to work.
[0018] A RJ-45 connector can be applied to the interface between
the KVM switch and the signal cable, as well as the interface
between the signal cable and the module of the present invention.
The KVM device can have 32 RJ-45 connecting ports (RJ-45 female
connectors) in a 1U system rack to connect up to 32 computers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The present invention will be further described in details
in conjunction with the accompanying drawings.
[0020] FIG. 1a illustrates a conventional CAT 5 based KVM
system.
[0021] FIG. 1b illustrates a conventional CAT 5 cable.
[0022] FIG. 2a illustrates a KVM system in accordance with the
present invention.
[0023] FIGS. 2b and 2c illustrate wires of signal cables in
accordance with the present invention.
[0024] FIG. 3a illustrates a first embodiment implemented with a
KVM system in accordance with the present invention.
[0025] FIG. 3b illustrates a module in FIG. 3a in accordance with
the present invention.
[0026] FIG. 3c illustrates a KVM system for the IO signal and the
video signal accessible to a network.
[0027] FIG. 4 illustrates a second embodiment implemented with a
KVM extender in accordance with the present invention.
[0028] FIG. 5 illustrates a third embodiment implemented with a
matrix KVM system in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0029] In accordance with the present invention, a single-ended
video signal is transmitted. Please refer to FIG. 2a. A KVM system
of the present invention comprises a module 28, a KVM switch 29 and
a signal cable 23. As shown, a console 12 receives a video signal
from a computer 11. The video signal directly transmitted over
wires is the so-called single-ended video signal. As shown in FIG.
2a, a single-ended video signal from the computer 11 passes through
the module 28 and the KVM switch 29 to the console 12 via the
signal cable 23. The single-ended video signal is not encoded or
decoded. That is, the video signal transmitted from the computer to
the KVM switch has not been transformed to differential
signals.
[0030] Please refer to FIG. 2b and FIG. 2c, which illustrate wires
of the signal cable 23. The single-ended video signal, for example,
a VGA signal from a VGA port of the computer, comprises R, G, B,
H-sync and V-sync signals. When the single-ended video signal
passes through the signal cable 23, the signal cable 23 comprises 5
wires separated for transmitting the R, G, B, H-sync and V-sync
signals corresponsively, and one wire grounded.
[0031] By transmitting the single-ended video signal, the KVM
system of the present invention does not need a video encoder
circuit and/or a video decoder circuit, therefore, reducing cost
can be achieved. For short distance communication, the image
quality of the KVM system of the present invention is better than
the conventional CAT 5 based KVM system for the reason that the
video signal transmitted by utilizing differential signaling
transmission in short distance will be over excited.
[0032] Please refer to FIG. 2a. The computer 11 is communicated
with the console 12 by transmitting an input/output (IO) signal,
e.g. a keyboard (KB) signal, a mouse (MS) signal, an USB storage
data signal, a DDC signal, and/or an audio signal through the KVM
system of the present invention. These IO signals are collected as
parallel signals by a controller 261. The parallel signals are
converted into a serial signal by a signal converter 269.
Generally, the signal converter 269 can be employed as a universal
asynchronous receiver/transmitter (UART), which is a piece of
computer hardware that translates data between parallel and serial
forms. The UART converts the IO signals (parallel form) into an
UART signal (serial form). The signal cable 23 transmits the serial
signal to the module 28. The module 28 comprises a signal converter
259 for converting the serial signal to the parallel signals. The
parallel signals are transmitted to a controller 251. The signal
converter 259 also can be employed as the UART for converting the
UART signal (serial form) into the IO signals (parallel form). The
controller 251 controls the IO signals and outputs the IO signals
to the computer 11. The signal converter 259 and the signal
converter 269 can be employed as UART ICs, for example, MAX3110E or
MAX3140, manufactured by Maxim Integrated Products. The IO signal
from the computer 11 is operated in reverse path. For example, the
IO signal from the computer 11 passes through the module 28, the
signal cable 23 and the KVM switch 29 in order until received by
the console 12. The signal cable 23 has a first RJ-45 connector at
its first end for connecting the KVM switch 29 and a second RJ-45
connector at its second end for connecting the module 28. On the
other hand, the KVM switch 29 has a plurality of RJ-45 female
connectors to match the first end of the signal cable 23. The
signal cable 23 further has 8 signal wires for carrying the
single-ended video signals and UART signal (serial form). At least
6 of the 8 signal wires are untwisted and separated.
[0033] Please refer to FIG. 2b also with FIG. 2a. The serial signal
can be transmitted by utilizing non-differential signaling
transmission. The signal cable 23 has two separated wires for
transmitting uni-directional serial signals, for example, TxD and
RxD signals abided by the standard of RS-232 in full-duplex mode,
and one grounded wire for grounding. The grounded wire is also used
when transmitting the single-ended video signal.
[0034] Please refer to FIG. 2c also with FIG. 2a. The serial signal
can be transmitted by utilizing differential signaling
transmission. The signal cable 23 has a twisted pair of wires for
transmitting the serial signal. The serial signal is
bi-directionally transmitted in each wire of the twisted pair, so
the serial signal is called a bi-directional serial signal. For the
UART signal mentioned above, by differential signaling, the UART
signal is signaled as U.sub.+ and U.sub.- in the twisted pair as
shown. For example, the UART signal abided by the standard of
RS-485 is applicable. Compared with the non-differential signaling
transmission, the differential signaling transmission is beneficial
for much higher speed to transmit the serial signal.
[0035] Please refer to FIGS. 3a and 3b. The first embodiment of a
KVM system in accordance with the present invention is illustrated.
As shown in FIG. 3a, there are 4 computers, computer 112, computer
114, computer 116 and computer 118, coupled to the KVM switch 29.
Each computer is accompanied with a module. One module couples one
computer to the KVM switch 29. The computer 112 is accompanied with
a module 282, the computer 114 with a module 284, the computer 116
with a module 286, and the computer 118 with a module 288. The KVM
switch 29 has a video switch 311 to switch to one of the computers
and to route a single-ended video signal from the one of the
computers to a monitor for display. The KVM switch 29 has a
controller 261 to manage and process an IO signal so as to select
which computer the IO signal is to be transmitted to. The IO signal
may come from a keyboard, a mouse, a speaker, a microphone, an USB
mass storage, and/or other USB devices etc. The controller 261
comprises a field-programmable gate array (FPGA) 2611 to manage and
a CPU 2613 to process the IO signal in accompany with a Flash
memory 2615 and a SDRAM 2617. The FPGA 2611 further converts the IO
signal from aforesaid console devices into an UART signal. The FPGA
2611 can be replace by PLD (Programmable Logic Device), PAL
(Programmable Array Logic), GAL (Generic Array Logic), CPLD or
ASIC. The KVM switch 29 has 4 RS485 transceivers 2692, 2694, 2696
and 2698, correspondingly connected to the modules 282, 284, 286
and 288, respectively via signal cables 232, 234, 236, and 238, for
transmitting and receiving the UART signal between the KVM switch
29 and the modules. The RS-485 transceivers can be replaced by
RS-232 transceivers. In addition, the IO signal may also comes from
the computers 112, 114, 116, and 118 and be transmitted to the
console.
[0036] Please refer to FIG. 3b. The module 282 is illustrated. The
other modules mentioned above are identical to the module 282. The
module 282 has a controller 251 to control the IO signal from the
computer 112 or to the computer 112. The controller 251 comprises a
FPGA 2511, a CPU 2513, a Flash memory 2515, a SDRAM 2517 and an
EEPROM 2519. The EEPROM 2519 can store monitor ID. For USB
interfaces, the IO signal is transmitted to the CPU 2515 and then
passed to the FPGA 2511. For PS/2 interfaces, the IO signal is
directly transmitted to the FPGA 2511. The IO signal is further
converted to the UART signal by the FPGA 2511. The FPGA 2511 can be
replace by PLD (Programmable Logic Device), PAL (Programmable Array
Logic), GAL (Generic Array Logic), CPLD or ASIC. The module 282 has
a RS-485 transceiver 2592 for transmitting (or receiving) the UART
signal to (or from) the corresponding RS485 transceiver 2692 of the
KVM switch 29. The RS-485 transceiver 2592 can be replaced with a
RS-232 transceiver, correspondingly, the RS485 transceiver 2692 of
the KVM switch 29 replaced with a RS-232 transceiver, too.
[0037] Please refer to FIG. 3c. The IO signal and the video signal
are accessible to a network. The IO signal from the computers 112,
114, 116, 118 can be transmitted to the network. The video signal
from the computers 112, 114, 116, 118, also can be transmitted to
the network. As shown in FIG. 3c, the video signal is converted
into digital signal by an analog-to-digital (AD) converter 33. In
FIG. 3c, a network controller 34, for example, a network interface
controller (NIC), is used to manage computers on the network to
access to this KVM system 39. Accordingly, the computers on the
network as console computers can access and control the computers
112, 114, 116, 118. The KVM system 39 with features shown in FIG.
3c is implemented as KVM over IP products.
[0038] Please refer to FIG. 4. The second embodiment in accordance
with the present invention is implemented with a KVM extender. The
KVM extender, which allows access to a computer 11 from a console
device in the distance, comprises a local unit 48 and a remote unit
49. The local unit 48 is coupled with the computer 11 to transmit a
signal-ended video signal and an IO signal to the remote unit 49
via a signal cable 43. The signal cable 43 has a first RJ-45
connector at its first end for connecting the local unit 48 and a
second RJ-45 connector at its second end for connecting the remote
unit 49. The local unit 48 comprises a FPGA 4511, a CPU 4513, a
Flash memory 4515, a SDRAM 4517 and a RS-485 transceiver 4590, and
the remote unit 49 comprises a FPGA 4611, a CPU 4613, a Flash
memory 4615, a SDRAM 4617 and a RS-485 transceiver 4690. The local
unit 48 further comprises a video buffer 4118 for buffering the
single-ended video signal so as the remote unit has a video buffer
4119. The CPU 4613 of the remote unit 49 can control the gain of
the single-ended video signal. For a short distance, the FPGA 4511
of the local unit 48 and the FPGA 4611 of the remote unit 49 can
achieve direct high speed data link (HSDL), thus RS-485
transceivers 4590, 4690 can be omitted. For direct HSDL mode, the
RS-485 transceivers 4590, 4690 are waived. For example, the FPGA
4511 and FPGA 4611 can be a master device and a slave device in a
two wire communication protocol, such as, I.sup.2C.
[0039] Please refer to FIG. 5. The third embodiment in accordance
with the present invention is implemented with a matrix KVM system,
which allows multiple users control computers simultaneously and
independently. The computers can be connected through a combination
of multiple matrix KVM switches. As shown in FIG. 5, a computer 11
is coupled to console devices (KB/MS/monitor/USB/Audio) via a first
module 58, a matrix KVM switch 59, and a second module 50. The
first module 58 comprises a FPGA 5511, a CPU 5513, a Flash memory
5515, a SDRAM 5517, a RS-485 transceiver 5590 and a video buffer
5118, the matrix KVM switch 59 comprises a FPGA 5611, a CPU 5613, a
Flash memory 5615, a SDRAM 5617, numbers of RS-485 transceiver,
e.g. a RS-485 converter 5670, 5680, 5690, and 5699, and a video
buffer 5119, and the second module 50 comprises a FPGA 5011, a CPU
5013, a Flash memory 5015, a SDRAM 5017, a RS-485 transceiver 5090
and a video buffer 5110. The matrix KVM switch 59 has a video
matrix 5111 coupled to the FPGA 5611 to manage the single-ended
video signal and route the single-ended video signal from one of
computers to a monitor for display. A multiplex can be employed as
the video matrix 5111. For an IO signal from a computer 11, the IO
signal is converted by the FPGA 5511, transmitted by the RS-485
transceiver 5590, received by the RS-485 transceiver 5690,
converted by the FPGA 5611, transmitted by the RS-485 transceiver
5670, received by the RS-485 transceiver 5090, and converted by the
FPGA 5011 in order, to the console. There are a first signal cable
531 for connecting the first module 58 to the matrix KVM switch 59,
and a second signal cable 532 for connecting the matrix KVM switch
59 to the second module 50. The first signal cable 531 has a first
RJ-45 male connector at its first end for connecting the matrix KVM
switch 59 and a second RJ-45 male connector at its second end for
connecting the first module 58. One the other hand, the KVM switch
59 has a plurality of RJ-45 connecting ports (female connectors) to
match the first end of the first signal cable. The first signal
cable 531 further has 8 signal wires for carrying the single-ended
video signal and UART signal. At least 6 of the 8 signal wires are
untwisted and separated. The second signal cable 532 is similar to
the first signal cable 531.
[0040] The UART signal mentioned above can be transmitted by
utilizing non-differential signaling transmission, e.g. RS-232,
which communicates in full-duplex mode, or by differential
signaling transmission e.g. RS-485, which communicates in
half-duplex mode. The signal cable for connecting KVM devices, e.g.
a module, a KVM switch, a local unit, a remote unit and a matrix
KVM switch etc., may have a RJ-45 male connector.
[0041] While the preferred embodiments of the present invention
have been illustrated and described in details, various
modifications and alterations can be made by persons skilled in
this art. The embodiments of the present invention are therefore
described in an illustrative but not restrictive sense. It is
intended that the present invention should not be limited to the
particular forms as illustrated, and that all modifications and
alterations which maintain the spirit and realm of the present
invention are within the scope as defined in the appended
claims.
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